This invention relates generally to a polyamine compound useful in epoxy-based coating compositions and thermosetting composites.
Typically, formulating epoxy resins with highly functional curing agents (hardeners) leads to short working lives, high formulation viscosity and brittle parts after curing. These negative effects are all driven by the high functionality of the curing agent. It is well known that in step growth polymerization, the degree of polymerization, Xn, and the critical extent of reaction (gel point−pc) are directly linked to the functionality of the polymerizing system: Xn=2/(2−pfavg) where p is the extent of reaction and favg is the average functionality and pc=2/favg. Thus systems with a high average functionality will reach high molecular weights and gel at a lower degree of polymerization than those with a low average functionality. U.S. Pat. No. 4,293,682 discloses use of tetra- and penta-functional amines as curing agents.
While low functionality curing agents will provide longer pot lives, these lead to final cured networks with low crosslink densities and poor thermal and mechanical properties. This inverse relationship between highly functional monomers needed for final part properties and low functionality monomers for enhanced working time requires a compromise in formulating epoxies. Anything that can be done to enhance working time without adversely affecting the final part properties would be advantageous.